1. Field of the Invention
This invention generally relates to an apparatus, system, and method for improved telephony and, more particularly, to an apparatus, system, and method for reducing or eliminating echo when communicating over packet-switched telephone connections.
2. Description of Related Art
Digital circuit switches have traditionally been used to route voice traffic and low-throughput data traffic but advances in electronics have made packet-switched digital connections, such as Voice over Internet Protocol, increasingly cost-effective.
Circuit switches traditionally provided a physical, dedicated path, called a time slot, for a call when it went through the switching matrix. Because this path was dedicated to the call, no other callers could use the selected switch path until the call ended. This concept of a dedicated path guaranteed high-quality, almost error-free transmission for the call.
Packet switches, in contrast, do not use dedicated paths, but evolved in the 1970s to handle the variable bit rates of data transmission bursts. Packet switches take a user's data stream, break it down into smaller segments, called packets, add network control information, and then transmit the packets through the network in bursts. When a burst of data comes in, switching resources are assigned for that burst, with the resources being shared on an as-needed, first-come, first-served basis. At the end of the burst of data, the resources are available for the next burst of data.
The steady rise in signal processing power, memory capacity, operating speed, and error correction has allowed packet-switched networks to handle the real-time demands of voice traffic. With the huge increase of Internet users and data transmissions over communication networks in the past several years, telecommunication companies and Internet providers are moving to route both voice and data traffic, as well as Internet traffic, over packet-switched networks.
A disadvantage of packet-switched networks has been that the amount of real-time processing required to control the packets has been enormous. Accordingly, the real-time processing has introduced a certain amount of delay in moving a packet through the network. Thus, packet-switched connections necessarily add a perceptible amount of delay to signal transmission, while traditional circuit-switched connections do not create perceptible delay since a path remains fixed once a call is set up. This delay makes objectionable even a small amount of coupling of the received voice signal into the transmitted signal, which causes a caller to hear an echo of his/her own voice. Most callers find such an echo, even one that is not loud, to be distracting and annoying.
Telephone headsets commonly couple more of the received signal into the transmitted signal than is optimal for modern, packet-switched connections. Similarly, many handsets in use today were not designed with the requirements of packet-switched telephony in mind, and therefore couple more of the received signal into the transmitted signal than is optimal.
Different methods have been used to reduce echo associated with telephones. One method has been to change the mechanical and acoustic characteristics of the headset to reduce coupling between the receive signal and the transmit signal. Disadvantageously, this method requires compromising other desirable characteristics of the headset, such as wearing comfort, weight, small size, and low cost. Furthermore, this method requires the owner of an existing headset to purchase a new one.
A second method has been to suppress undesired echoes using equipment or software within the telephone network between the telephones in use. This method has included either digital hardware or digital signal processing software built into the network equipment to help solve the fundamental delay problems for stream voice, video, or raw data. Unfortunately, network echo reduction equipment is commonly optimized for handling echoes that originate within the network, whose characteristics remain relatively constant for the duration of a single call. However, the undesired signal coupling in a headset or handset can vary rapidly during a call, since small movements of the user can affect the coupling. This rapid variation greatly reduces the effectiveness of network echo reduction equipment. Accordingly, such network equipment cannot accommodate the complex characteristics of the adjuncts connected to the user side of these gateways or packet-switched networks.
A third method has been to suppress undesired echoes using equipment designed into the telephone itself. However, many phones in use today lack such means to reduce the echo caused by undesired coupling. Furthermore, when the user attempts to use a telephone headset or a telephone handset which is different from that provided with the telephone originally, the caller can hear undesirable echo.
Therefore, there is a need for an apparatus, system, and method that allows for a reduction in echo when using a variety of headsets and handsets in conjunction with packet-switched networks without having to purchase new headsets or handsets.